-LRB- CNN -RRB- -- The bodies of two dolphins and the head of another have washed up along the Gulf Coast , raising red flags for federal investigators already looking into roughly half a dozen dolphin killings .

Excluding the latest three , the bodies of at least seven dolphins have turned up this year along a 120-mile stretch of the Gulf Coast from Louisiana to Florida . Some were shot , stabbed and mutilated .

It 's unclear whether the latest three deaths are related to those killings , but investigators are exploring that possibility .

Moby Solangi , lead biologist of The Institute of Marine Mammal Studies in Gulfport , Mississippi , performed necropsies on nine of the dead marine mammals and will do the 10th on Wednesday .

`` We have submitted those results to the federal enforcement officers , who are going to do additional exams or testing to further clarify the cause of death , '' he said .

Citing the ongoing criminal investigation , Solangi declined to elaborate on the results .

The Marine Mammal Protection Act states that anyone convicted of killing a dolphin could be sentenced to one year in prison and fined up to $ 100,000 . The law also makes it a crime to feed dolphins in the wild .

The remains of the latest three dolphins were found in Mississippi .

A group of bird surveyors discovered an adult dolphin head on the west tip of Horn Island on Friday . On Saturday , someone found the body of a 1-year-old male dolphin on the beach in Gulfport . On Tuesday , another dolphin was found dead in Bay St. Louis ; a teacher at a boarding school saw the animal and reported it .

It 's not unusual to see dolphin bodies , or even parts of bodies , wash up . What is unusual is evidence of human interaction as the cause of death , as appeared to be the case in the first seven situations .

The first dolphin was found January 8 with a bullet wound on Deer Island , near Biloxi , Mississippi . In June , a bottlenose dolphin was found in Perdido Bay , Florida , near the Florida-Alabama state line , with a screwdriver stuck in its head . In September , one was found on Elmers Island , Louisiana , with a gunshot wound . On October 10 , a dolphin was found on the beach in Dauphin Island , Alabama , with its fluke cut off .

The list continues .

On November 6 , a dolphin was found dead with numerous cuts near Ocean Springs , Mississippi . Three days later , two more were discovered : another one with bullet wounds near Ocean Springs , and one on Ship Island , a remote barrier island off Biloxi , Mississippi , with its jaw cut off .

Authorities are still trying to determine whether a dead dolphin found November 2 , in Bayou Julia , Louisiana , is linked to the other killings .

Jeff Radonski , a deputy special agent for the National Oceanic and Atmospheric Administration , which is leading the investigation , spoke last month about the deaths .

`` We need to have witnesses come forward . We need public input and information , '' he said .

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Two bodies and the head of another dolphin are found in Mississippi

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Investigators are looking into whether the deaths could to linked to other dolphin killings

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Roughly half a dozen dolphins have been shot , stabbed or mutilated this year